The Bacillus Calmette-Guérin vaccine was named after the French scientists who developed it and was first used in 1921.
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The BCG, an old vaccine but the only one against tuberculosis, is more effective than was thought, offering protection for at least 20 years, a new study shows.

BCG vaccination used to be routine in all secondary schools in the UK for young teenagers, but in recent years it has been given only to those at risk, such as children living in inner-city areas with relatively high TB rates.

The vaccination was thought to work for only 10 to 15 years, but a new study shows that the protective effect of the BCG has been underestimated. Researchers from the London School of Hygiene and Tropical Medicine say they have found that it protects half of those given it at the age of 12 or 13 for at least 20 years and then the effects wane.

The Bacillus Calmette-Guérin vaccination, named after the French scientists who developed it, was first used in 1921, but in spite of the passage of time and the limited protection it offers, there is still no other.

The LSHTM researchers say that knowing about the longer protective effect of the vaccine will reassure those who had it in the UK when they were children and be helpful in countries with a high TB rate. It strengthens the argument for using the BCG to protect children in heavily-affected regions such as parts of central and western Africa, east Asia and the Pacific, where the take-up is low.

TB is a major, and preventable, cause of death and disease which mainly affects the lungs. About 2 to 3 three billion people in the world are infected with Mycobacterium tuberculosis, 10% of whom become ill as a result. In 2015 there were an estimated 10.4m new cases of TB and 1.8m deaths globally.

Lead author Dr Punam Mangtani, associate professor in Epidemiology said: “For those who had the BCG at school, knowing that it lasts longer than was assumed is reassuring. They are a bit more protected than was originally thought. This helps support a vaccine that is not often considered as being as important as some of the other infant vaccines.”

The results would also provide a yardstick against which any badly-needed new TB vaccines could be measured, she said. There are at least 10 under development, but the most recent failed to show any protection in trials.